Question

Observe the picture given in Fig. carefully.
A patch of light is observed at B, when the torch is lighted as shown. Which of the following is kept at position A to get this patch of light?

A. A wooden board
B. A glass sheet
C. A mirror
D. A sheet of white paper.

Answer 1

Hint: We can observe in the diagram that the light from the torch is getting reflected from the slab towards the screen. All light rays get completely reflected. The slab would be made of material which has a property of reflecting the entire light rays incident on them.

Complete answer:
We are given a torch which emits light towards the slab A. The light rays get reflected towards the screen B. There is no transmission or absorption of light taking place. This type of property of reflection is possessed only by a mirror which reflects the entire light rays incident on it.

So, the correct answer is “Option C”.

Additional Information:
The reflection of light is governed by the following two laws of reflection of light.
1. The first law says that the incident ray and the reflected ray along with the normal at the point of incidence will always lie in the same plane.
2. The angle made by the incident ray with respect to the normal at the point of incidence will be the same as the angle made by the reflected ray with respect to the normal at the point of incidence.
The light falling on a mirror obeys all these laws.

Note:
A wooden board and a sheet of white paper will tend to absorb the light rays incident on them and there will be no light obtained on the screen in that case. In the case of a glass sheet, we will observe that light rays will undergo refraction instead of reflection and all light will pass through the glass sheet.